Although there is ample evidence to indicate that proteolysis plays a decisive role in the cellular proliferation and the invasiveness of cancer tissue, the specific enzymes responsible for either one or both of these processes have yet to be isolated and studied and their function clearly defined. The major objective of this proposal is to isolate and characterize these proteases from tumor tissue, or tumor cells grown in culture, and to establish their role in reaction pathways which ultimately lead to uncontrolled growth and invasiveness. The purified enzymes will be characterized with respect to physicochemical properties, kinetic properties, substrate specificity, and inhibition by protease inhibitors. The purified proteases will then be tested for their ability to mimic the effects produced by viral transformation of normal cells as revealed by (1) loss of contact inhibition, (2) agglutinability by plant lectins, (3) decrease in levels of cyclic AMP, and (4) invasiveness towards tissue explants. The effect of protease inhibitors in counteracting these effects will also be investigated.